Tunable antenna structure and wireless communication device employing same

Abstract

A tunable antenna structure includes an antenna, a first switch circuit and a second switch circuit. The antenna structure includes a feeding point configured to feed current signal and a grounding point configured to be grounded. The first switch circuit includes a first plurality of loads and a first switch electronically coupled to the feeding point and the first plurality of loads. The first switch is configured to selectively couple one of the first plurality of loads to the feeding point. The second switch circuit includes a second plurality of loads and a second switch electronically coupled to the grounding point and the second plurality of loads. The second switch is configured to selectively couple one of the second plurality of loads to the grounding point.

What is claimed is: 
     
       1. A tunable antenna structure comprising:
 an antenna component comprising a feeding point configured to feed current signal and a grounding point configured to be grounded; 
 a first switch circuit comprising a first plurality of loads and a first switch electronically coupled to the feeding point and the first plurality of loads; the first switch configured to selectively couple one of the first plurality of loads to the feeding point; 
 a second switch circuit comprising a second plurality of loads and a second switch electronically coupled to the grounding point and the second plurality of loads; the second switch configured to selectively couple one of the second plurality of loads to the grounding point; 
 wherein one terminal of each of the first groups of loads is grounded, another terminal of each of the first plurality of loads is electronically coupled to the first switch; 
 wherein one terminal of each of the second groups of loads is grounded, another terminal of each of the second plurality of loads is electronically coupled to the second switch; 
 wherein the first plurality of loads comprises a first inductor, a second inductor, a third inductor, and a fourth inductor; the second plurality of loads comprises a fifth inductor and a zero ohm resistor; when the first switch couples the first inductor with the feeding point and the second switch couples the fifth inductor with the grounding point, the tunable antenna structure is configured to receive/send wireless signals at a first frequency band; wherein when the first switch couples the second inductor with the feeding point and the second switch couples the fifth inductor with the grounding point, the tunable antenna structure is configured to receive/send wireless signals at a second frequency band; wherein when the first switch couples the third inductor with the feeding point and the second switch couples the fifth inductor with the grounding point, the tunable antenna structure is configured to receive/send wireless signals at a third frequency band; and wherein when the first switch couples the fourth inductor with the feeding point and the second switch couples the zero ohm resistor with the grounding point, the tunable antenna structure is configured to receive/send wireless signals at a fourth frequency band. 
 
     
     
       2. The tunable antenna structure of  claim 1 , wherein a value of the first inductor is from 8.2 nH to 9.1 nH; a value of the second inductor is from 4.7 nH to 5.6 nH; a value of the third inductor is from 3.9 nH to 4.7 nH; a value of the fourth inductor is from 1.2 nH to 2 nH; a value of the fifth inductor is from 68 nH to 120 nH. 
     
     
       3. The tunable antenna structure of  claim 1 , further comprising an impedance matching circuit and a signal source, wherein the impedance matching circuit comprises a first capacitor, a second capacitor and an inductor, the inductor and the first capacitor are electronically coupled in series between the signal source and a node between the feeding point and the first switch; one terminal of the second capacitor is electronically coupled to a node between the signal source and the inductor, another terminal of the second capacitor is grounded. 
     
     
       4. The tunable antenna structure of  claim 3 , wherein a value of the inductor is from 3.9 nH to 5.1 nH; a value of the first capacitor is from 1.2 pF to 2.2 pF; a value of the second capacitor is from 1.2 pF to 2.2 pF. 
     
     
       5. A wireless communication device comprising:
 a signal source; 
 a tunable antenna structure comprising:
 an antenna component comprising a feeding point electronically coupled to the single source; 
 a first switch circuit comprising a first plurality of loads and a first switch electronically coupled to the feeding point and the first plurality of loads; the first switch configured to selectively couple one of the first plurality of loads to the feeding point; 
 a second switch circuit comprising a second plurality of loads and a second switch electronically coupled to the grounding point and the second plurality of loads; 
 wherein one terminal of each of the first groups of loads is grounded, another terminal of each of the first plurality of loads is electronically coupled to the first switch; 
 wherein one terminal of each of the second groups of loads is grounded, another terminal of each of the second plurality of loads is electronically coupled to the second switch; 
 wherein the second switch is configured to selectively couple one of the second plurality of loads to the grounding point; the first plurality of loads comprises a first inductor, a second inductor, a third inductor, and a fourth inductor; the second plurality of loads comprises a fifth inductor and a zero ohm resistor; wherein when the first switch couples the first inductor with the feeding point and the second switch couples the fifth inductor with the grounding point, the tunable antenna structure is configured to receive/send wireless signals at a first frequency band; wherein when the first switch couples the second inductor with the feeding point and the second switch couples the fifth inductor with the grounding point, the tunable antenna structure is configured to receive/send wireless signals at a second frequency band; wherein when the first switch couples the third inductor with the feeding point and the second switch couples the fifth inductor with the grounding point, the tunable antenna structure is configured to receive/send wireless signals at a third frequency band; and wherein when the first switch couples the fourth inductor with the feeding point and the second switch couples the zero ohm resistor with the grounding point, the tunable antenna structure is configured to receive/send wireless signals at a fourth frequency band. 
 
 
     
     
       6. The wireless communication device of  claim 5 , wherein a value of the first inductor is from 8.2 nH to 9.1 nH; a value of the second inductor is from 4.7 nH to 5.6 nH; a value of the third inductor is from 3.9 nH to 4.7 nH; a value of the fourth inductor is from 1.2 nH to 2 nH; a value of the fifth inductor is from 68 nH to 120 nH. 
     
     
       7. The wireless communication device of  claim 5 , further comprising an impedance matching circuit, wherein the impedance matching circuit comprises a first capacitor, a second capacitor and an inductor, the inductor and the first capacitor are electronically coupled in series between the signal source and a node between the feeding point and the first switch; one terminal of the second capacitor is electronically coupled to a node between the signal source and the inductor, another terminal of the second capacitor is grounded. 
     
     
       8. The wireless communication device of  claim 7 , wherein a value of the inductor is from 3.9 nH to 5.1 nH; a value of the first capacitor is from 1.2 pF to 2.2 pF; a value of the second capacitor is from 1.2 pF to 2.2 pF.